The present invention relates to circuitry which is operative to adjust the energizing input of a sensing circuit in order to stabilize the normal output of the sensing circuit. In this manner, adjustment of the sensing circuit reference level is carried out so as to compensate for drift in component values and changing ambient conditions which would cause fluctuations in the normal output of the sensing circuit. The adjustment circuit disclosed herein is preferably normally de-energized, and is capable of making the necessary adjustment to the sensing circuit input within a fraction of a second after being simultaneously energized and receiving a first input signal. Energization of the adjustment circuit is effected by a voltage regulation circuit which is normally inoperative to provide a regulated output voltage. Thus, standby power dissipation is minimized. The system disclosed herein may be employed, for example, in an automotive vehicle as a warning circuit operative to provide a signal when a seat is occupied but the associated seat belt is not buckled.